PROJECT SUMMARY Coronary heart disease, including acute myocardial infarction (AMI), is the leading cause of death in the United States. Because ST-elevation myocardial infarctions (STEMIs) require timely access to percutaneous coronary intervention (PCI), many communities have created systems of regionalized STEMI care in which designated hospitals provide emergent PCI capability at all times. Regionalization is likely to have unintended consequences on non-STEMI (NSTEMI) care as patients and emergency medical services providers may increasingly seek care at PCI centers, and both PCI and non-PCI centers may change their care of NSTEMI patients. As NSTEMIs outnumber STEMIs by up to three to one and have a higher one-year mortality than STEMIs, understanding the impact of regionalization on NSTEMI care and outcomes is essential for policymakers and health systems if they choose to implement cardiac care regionalization. Our goals in this proposal are three-fold: (1) to determine the extent to which STEMI regionalization is associated with de facto NSTEMI regionalization; (2) to determine whether treatment and outcomes differed for NSTEMI patients after regionalization; and (3) to measure the changes in disparities of health outcomes between vulnerable and general populations. We propose an approach that exploits a series of natural experiments in California. Using statewide non-public data from the California Office of Statewide Health Planning and Development from 2006 through 2012 (?280,000 NSTEMI patients) linked to Vital Statistics death data and a STEMI registry created by the PI for the parent grant, we will pursue a difference-in- differences approach to identify the association between regionalization and changes in treatment and outcomes. In Aim 1, we determine the extent to which regionalization changed the location at which NSTEMI patients received their care. We hypothesize that the proportion of NSTEMIs treated at PCI centers increased after regionalization. In Aim 2, we determine whether treatment and outcomes differed for NSTEMI patients treated at PCI centers versus non-PCI centers within regionalized communities, and whether outcomes improved for patients in regionalized compared to non-regionalized communities after regionalization. We hypothesize that outcomes improved at PCI centers and also in regionalized communities. To understand how changes in outcomes might occur, we will also measure the proportion of NSTEMI patients undergoing PCI; we hypothesize that this proportion changed similarly. In Aim 3, we will determine whether the changes in treatment and outcomes differed for vulnerable compared to general populations using a difference-in- difference-in-differences approach. We hypothesize that disparities between groups narrowed after regionalization.